1. Field of the Invention
The present invention relates to a photographing device for taking a photo of an image having a large light quantity ratio while a light quantity adjustment is partially made, and particularly to a photographing device, such as a digital still camera or a digital video camera, using an image pickup element, such as a CCD (charge coupled device), capable of suitably recording an image having a large light quantity ratio.
2. Description of the Related Art
At present, as a device for recording an image, a digital still camera, a video camera or the like is used in a wide range. In such a digital still camera or a video camera, a CCD image pickup element for outputting an output signal on the basis of the quantity of electric charge stored in response to the quantity of light received in a definite time, a CMOS image pickup element, or the like is mainly used, and the obtained output signal is A/D converted, so that an image can be digitized. Although this CCD image pickup element or the like generates a large output signal substantially in proportion to an increase of light quantity within a predetermined range, in the case of a predetermined light quantity or less, an output signal value corresponding to variation of the light quantity can not be obtained and an almost constant output signal value is outputted. Also in the case of exceeding a predetermined light quantity, an output signal corresponding to variation of the light quantity cannot be obtained and an almost constant output signal value is outputted.
That is, there is a limit in the range (dynamic range) of light quantity in which the quantity of storage electric charge substantially proportional to the quantity of light received by the CCD image pickup element or the like is generated, and there is a case where light quantity exceeding the dynamic range or below the dynamic range is received by the CCD image pickup element or the like, as in a backlight scene or a stroboscopic scene.
Thus, in the case where the backlight scene in which the light quantity of a main subject is insufficient against a background is photographed by using the CCD image pickup element or the like, the main subject to be photographed becomes a dark portion (shadow) or the background becomes a bright portion (highlight) in a photographed image, thus leading to dull shadow or washed-out highlight. In the case of the stroboscopic scene, the main subject becomes a bright portion (highlight) or the background becomes a dark portion (shadow), thus leading to dull shadow or washed-out highlight.
Incidentally, in the case where a print output image is outputted by printing an image which has a large light quantity ratio such as a backlight scene or a stroboscopic scene, and is recorded on a photosensitive material such as a film, to a printing paper, in order to prevent dull shadow or washed-out highlight in a part of the image, a well-known dodging processing is performed in an image processing device to reproduce a suitable image. Besides, also in a digital image reproducing device in which an image recorded on a photosensitive material such as a film is photoelectrically read to form digital image data and the digital image data is subjected to digital image processing to output as a print, a similar technique is proposed.
For example, Japanese Patent Unexamined Publication No. Hei. 10-13680 proposes an image processing device and an image processing method for giving an effect of conventionally well-known dodging processing by performing image processing of a digital image in which an intermediate density portion of the image is not changed, but a low density portion of the image and a high density portion thereof are independently compressed or expanded.
However, in the foregoing image processing device and the image processing method, after recording is once made on an image recording medium such as a film, an adjustment is made through the image processing. It is impossible to directly process a scene to be photographed before it is photoelectrically read.
Besides, since such an image processing device is very expensive, although a trader who receives a request for print output can possess it, it is very difficult for an individual to possess it.
Then, in a digital still camera or a video camera using a CCD image pickup element or the like, there is desired a photographing device in which before a scene to be photographed is photoelectrically read, light quantity is adjusted in response to a dynamic range of the CCD image pickup element or the like to take an image.
Under such circumstances, Japanese Patent Unexamined Publication No. Hei. 7-298276 proposes a multi-plate image pickup device in which when an image is photoelectrically picked up by a CCD image pickup element or the like, incident light carrying an image to be read is divided to change a ratio of incident light quantity and the light is received by the image pickup element. According to that, when the image pickup element receives the divided incident light, the light quantity can be separately adjusted, so that photographing with a wide dynamic range becomes possible.
However, since this image pickup device must include a plurality of image pickup elements corresponding to the respective divided incident lights, a device for dividing the incident light, a device for synthesizing images read by the respective image pickup elements, and the like, there are problems that the image pickup device itself becomes complicated, a cost becomes high, and a time required for processing image data becomes long.